The use of a tractor to drive multiple mower units is well documented in the patent literature. As early as 1925, Seeley, in U.S. Pat. No. 1,556,965, disclosed such a tractor lawn mower. Seeley's combination has multiple reel type mower units; and each unit therein has its own independent ground contact drive.
Moyer, in U.S. Pat. No. 1,900,726, which issued Mar. 7, 1933, discloses an improvement of Seeley's gang mower in which a short couple is provided between the tractor and each ground driven mower. Moyer's mower also includes a set of springs which are used to push draw bars holding the mowers to the ground, so that they can be held in contact with it whether or not the ground is uneven.
Arnold, in U.S. Pat. No. 4,370,846, which issued Feb. 1, 1983, discloses a gang mower having a mounting frame which is raised by the action of a single hydraulic cylinder.